The present invention is directed to the lubrication of delivery equipment and glass molds during the manufacture of molded glass articles.
In manufacturing molded glass articles, molten (i.e., viscous) glass is introduced into a mold of suitable configuration. The viscous glass is subsequently caused to conform to the shape of the internal surface of the mold and hardens. It is known in the art of glass article manufacturing that the presence of a lubricant between the glass and the mold is highly desirable to overcome the adherent characteristics of the viscous glass and to allow the glass to slide over the mold surface. Further, the lubricant facilitates the removal of the hardened glass article from the mold.
Traditionally, such molds have been lubricated by the application of a carbonaceous liquid called "swab dope" directly onto the interior surface of the mold prior to the introduction of the viscous glass. In operation, a lubricating device such as a lubricant spray means or a brush adapted to apply the lubricant is positioned adjacent to a glass article-forming station which may include several molds of identical configuration. The internal surfaces of the molds are lubricated with the lubricant (i.e., swab dope) prior to being filled with viscous glass after 50 to 250 pieces of glass have been processed. After the glass has hardened and the article thus formed removed, the swab dope either remains on the interior surface of the mold (retaining some of its lubricating characteristics for the next glass-filling operation) or is ultimately burnt off by contact with the viscous glass unless replenished by relubrication as above.
As an alternative to lubrication, semi-permanent mold precoatings have been applied to the molds. The precoatings function as a lubricant in facilitating the sliding of viscous glass over the metal surface of the mold.
A known device for delivering viscous glass to a mold is described in U.S. Pat. No. 3,672,860 (issued to Keller). As disclosed therein, a gob of viscous glass is initially shaped to conform to the mold while falling through a funnel mechanism toward the mold. The funnel mechanism includes an arrangement for spraying an internal surface of the mold with a lubricant prior to introduction of the viscous glass into the mold. In one embodiment of the device disclosed therein, the sequence of operation for lubricating the mold may be timed such that the lubricant spray incidentally impinges on an outside surface of the glass gob as the gob enters the mold while primarily lubricating the interior surface of the mold. Thus, in that particular embodiment of Keller, the internal surface of the glass mold and the external surface of the glass gob may be simultaneously lubricated after the gob has at least partially entered the mold.
Several problems, however, exist when molds are lubricated in the above-identified manner. Generally, a mold must be prepared to receive the viscous glass in an assembly line-type of process. On an Individual Section (I.S.) machine, the glass gob is introduced into a blank and then formed into a parison. A transfer arm flips the parison, and the parison is blown to conform to the shape of the final mold. A hardened glass product is then removed from the final mold. In other glass product manufacturing machines, a mold is conveyed into a position for receiving a glass gob. The glass-filled mold is then removed and a new mold is positioned to receive a subsequent glass gob.
If a particular cycle of the I.S. machine or other glass manufacturing machine is programmed for swabbing the molds, precise timing is required in order to lubricate the mold prior to the entry of the viscous glass. Problems associated with the precise timing for the mold lubrication are compounded in prior art lubrication methods which lubricate the mold before each glass-filling operation. Thus, a mold which was adequately lubricated for a first viscous glass-filling operation may be relubricated before a second viscous glass-filling operation, even if the mold does not require additional lubrication.
Further, a lubrication device, if employed, must be positioned near the mold. The close proximity of the lubrication device to the mold results in cramped quarters. The operator is exposed to heat, noise, fumes and moving machinery during swabbing. This problem becomes especially acute in operations in which the filled mold is to be conveyed away from the glass article-forming station.
The amount of lubricant applied to the mold must also be monitored in such operations. If an insufficient amount of lubricant is applied to the mold, the glass may stick to the internal surface of the mold. Such sticking may result in damage to the mold and the production of an article having an imperfect shape and/or exterior surface. If an excessive amount of lubricant is applied, a black residue of the lubricant may appear on the surface of the glass product. Such residue of lubricant on a glass article is unsightly and thus decreases the value and quality of the article. In addition, vapors from the lubricant form black deposits on other parts of the glass-forming apparatus.